Microwave high power phase shifter utilizing cascaded directional couplers and plasma thyratrons

ABSTRACT

A microwave high power phase shifter is formed by two pairs of cascaded short slot hybrids whose slots are filled by low pressure gaseous volumes. Activation of the gas to the plasma state provides single-bit phase shifting action in the milliwatt to megawatt power range.

United States Patent M/DPA A/VE Coldie [451 Apr. 2, 1974 1 MICROWAVEHIGH POWER PHASE [56] References Cited SHIFTER UTILIZING CASCADED UNITEDSTATES PATENTS DIRECTIONAL COUPLERS AND PLASMA 3,008,097 11/1961Tctenbaum et al 333/10 X THYRATRONS 3,229,205 1/1966 Pitts et a1. 333/10ux 5 Inventor; Han-y Comic Randaustown? 3,324,420 6/1967 Blachier et a1333/7 [73] Assignee: The United States of America as represented y theSecretary of the Primary ExammerPaul L. Gensler Air Force, Washington;DC.

22 Filed: May 9, 1973 [57] ABSTRACT A microwave high power phase shifteris formed by [21] Appl' 8 two pairs of cascaded short; slot hybridswhose slots are filled by low pressure gaseous volumes. Activation Cl.333/31 333/7 PL ofthe gas to the plasma state provides single-bit phase[51] Int. Cl. H0lp 1/18 shifting action in the milliwatt to megawattpower [58] Field of Search 333/7 R, 10, 31 A, 98 S, range.

2 Claims, 2 Drawing Figures TERM/M4750 fl/VM 17 MICROWAVE HIGH POWERPHASE SHIFTER UTILIZING CASCADED DIRECTIONAL COUPLERS AND PLASMATHYRATRONS BACKGROUND OF THE INVENTION The operation of short slotwaveguide hybrids is well known and their ability to operate as a unitycoupler when two are cascaded has been an important function in balancedduplexers at high power levels. The present invention uses a uniquecombination of four short slot hybrids whose common wall containss agas-filled quartz vial or a plasma thyratron switch to effect a highpower single-bit phase shift action. The RF voltage in the slot of ahybrid is known to be less than that in the midplane of the inputwaveguide. Thus, a gas filled vial/tube located in the slot will be in aregion of relatively low RF voltage, thus inhibiting an RF discharge.This inability to cause a discharge in a gas under the influence of RFelectric fields is referred to as holdoff. The higher the RF holdoffpotential, the greater will be the RF power that can be passed without adischarge. The plasma necessary for switching action would normally becreated by applying video pulses at low potentials to suitable gridslocated in the plasma thyratron tubes.

SUMMARY OF THE INVENTION delay will occur depending uponthe firingofthyratrons. In a modification, the extra line lengthis madeadjustable.

DESCRIPTION OF THE DRAWINGS FIG. l shows an embodiment of the inventionincluding four cascaded short slot hybrids, four associated thyratrons,and an inserted line length; and

FIG. 2 illustrates schematically a modification of FIG. 1 wherein anadjustable short slot hybrid is substituted for the aforesaid insertedline length.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Now referring to FIG.1, there-is shown four cascaded short slot hybrids II, 12, 13 and 14containing four gas-filled quartz vials l5, 16, 17 and 18 in theirrespective common-wall openings. At the input there is provided arm A,and at the output, arm B. Arms C and D are terminated with anyconventional RF absorbent material. By inserting transmission line 19with a preselected length l, a high power single-bit phase shifter isformed. Transmission line 19 is compatible with short slot hybrids.Vials 15, I6, 17 and 18 are connected to low potential video pulse 20,each pulse resulting in plasma for switching.

In the operation of the phase shifter, with power incident at arm A, theinput power splits in nybrid 11 and recombines in hybrid 12 in C' with Cand A decoupled. This action is well known and is covered in manypapers, as for example, Design Aspects of Short Slot Hybrids, by R. J.Mohr in Microwave Journal, published June, 1962, and The Short SlotJunction, by H. V. Riblet in IRE Proceedings, published February, 1952.After traveling the line length l, the same action occurs from D to 'Bin hybrids l3 and 14. When the plasma switches are active, thecommon-wall slots become conductors, the RF conductivity depending 0strongly on the electron density in the plasma, and the power incidentat arm A travels unperturbed to output arm B. The phase shift occursbecause of the difference in signal travel length in each path. Afurther adaptation is shown in FIG. 2, where the extra path length is Itis emphasized that the present invention provides a unique combinationof short slot hybrids containing active elements in the common-wall slotregion (such as gas vials, triggered plasma thyratrons, or other activeelements). A single-bit two-part waveguide phase shifter is formed whichwill operate over a broad range of power levels. The phase shiftmagnitude can be made trimmable by using a short slot hybrid with gangedplungers as the added line length.

What is claimed is:

1. A microwave high power phase shifter comprised of first, second,third and fourth thyratrons normally in the passive state, first,second, third and fourth short slot hybrids cascaded in the recitednumerical sequence, said short slot hybrids having a common-wall with anopening in said common-wall of each of said short slot hybrids, an inputRF power and output arm at said first and fourth hybrid, respectively, aterminated arm at each of said firstand fourth hybrids, a transmissionline of preselected length in accordance with a desired phase shift,said transmission line being .inserted at the junction of said secondand third short shift action.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, ,93Dated pril 2, 197

Inventor-(n) Harry Goldie It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

On front; age, after Data Element Identifier [19] change "Coldie"'toGoldie On front page, after Data Element Identifier [75] chenge"'Coldie"to Goldie Signed and sealed this 5th day of November 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents

1. A microwave high power phase shifter comprised of first, second,third and fourth thyratrons normally in the passive state, first,second, third and fourth short slot hybrids cascaded in the recitednumerical sequence, said short slot hybrids having a common-wall with anopening in said common-wall of each of said short slot hybrids, an inputRF power and output arm at said first and fourth hybrid, respectively, aterminated arm at each of said first and fourth hybrids, a transmissionline of preselected length in accordance with a desired phase shift,said transmission line being inserted at the junction of said second andthird short slot hybrids, each of said openings in each of said shortslot hybrids containing one of said thyratrons, each of said thyratronsbeing located in each of its respective openings to be in a region ofrelatively low RF voltage to inhibit an RF discharge, and means to videopulse said thyratrons to provide plasma therein for switching to effecta high power single-bit phase shift action.
 2. A microwave high powerphase shifter as described in claim 1 wherein said inserted transmissionline is adjustable to provide a trimming of said phase shift action.